Technical Field
The present disclosure relates to an aluminum alloy conductor wire used as a conductor of an electric wiring structure, an aluminum alloy stranded wire, a coated wire, a wire harness, and a method of manufacturing an aluminum alloy conductor wire.
Background
In the related art, a so-called wire harness are being used as an electric wiring structure for transportation vehicles such as automobiles, trains, and aircrafts, or an electric wiring structure for industrial robots. The wire harness is a member including electric wires each having a conductor made of copper or copper alloy and fitted with terminals (connectors) made of copper or copper alloy (e.g., brass). With recent rapid advancements in performances and functions of automobiles, various electrical devices and control devices installed in vehicles tend to increase in number and electric wiring structures used for devices also tends to increase in number. On the other hand, for environmental friendliness, lightweighting of transportation vehicles is strongly desired for improving fuel efficiency of transportation vehicles such as automobiles.
As one of the measures for achieving lightweighting of transportation vehicles, there have been, for example, continuous efforts in the studies of using aluminum or aluminum alloys as a conductor of an electric wiring structure, which is more lightweight, instead of conventionally used copper or copper alloys. Aluminum has a specific gravity of about one-third of a specific gravity of copper and has a conductivity of about two-thirds of a conductivity of copper (in a case where pure copper is a standard for 100% IACS, pure aluminum has approximately 66% IACS). An aluminum conductor wire rod needs to have a cross sectional area of approximately 1.5 times greater than that of a copper conductor wire rod to allow the same electric current as the electric current flowing through the copper conductor wire rod to flow through the pure aluminum conductor wire rod. Even if an aluminum conductor wire rod having an increased cross section as described above is used, an aluminum conductor wire rod has a mass of about half the mass of a pure copper conductor wire rod. Therefore, it is advantageous to use an aluminum conductor wire rod considering lightweighting. Note that, “% IACS” represents a conductivity when a resistivity 1.7241×10−8 Ωm of International Annealed Copper Standard is taken as 100% IACS.
However, it is known that pure aluminum wire rods, typically an aluminum alloy wire rod for transmission lines (JIS (Japanese Industrial Standard) A1060 and A1070), is generally poor in its durability to tension, shock resistance, and bending characteristics. Therefore, for example, it cannot withstand a load abruptly applied by an operator or an industrial device while being installed to a car body, a tension at a crimp portion of a connecting portion between an electric wire and a terminal, and a cyclic stress loaded at a bending portion such as a door portion. On the other hand, an alloyed material containing various additive elements added thereto is capable of achieving an increased tensile strength, but conductivity may decrease due to a solution phenomenon of the additive elements into aluminum, and because of excessive intermetallic compounds formed in aluminum, a wire break due to the intermetallic compounds may occur during wire drawing. Therefore, it is essential to limit or select additive elements to provide sufficient elongation characteristics to prevent a wire break, and it is further necessary to ensure a conductivity and a tensile strength equivalent to those in the related art.
For example, aluminum alloy wire rods containing Mg and Si are known as high strength aluminum alloy wire rods. A typical example of this aluminum alloy wire rod is a 6xxx series aluminum alloy (Al—Mg—Si based alloy) wire rod. Generally, the strength of the 6xxx series aluminum alloy wire rod can be increased by applying a solution treatment and an aging treatment, and thus, when manufacturing a fine wire such as a wire having a wire size of less than or equal to 1.5 mm using a 6xxx series aluminum alloy wire rod, the strength can be increased by applying a solution heat treatment and an ageing treatment.
For example, Japanese Patent No. 4986252, Japanese Patent No. 4986251, Japanese Laid-Open Patent Publication No. 2010-163677 and Japanese Laid-Open Patent Publication No. 2010-163676 disclose a conventional 6xxx series aluminum alloy wire used for an electric wiring structure of the transportation vehicle and a manufacturing method thereof. Japanese Patent No. 4986252 discloses a method of manufacturing a 6xxx series aluminum alloy wire in which steps of casting and rolling, wire drawing, intermediate heat treatment, wire drawing and solution (recrystallization) heat treatment are performed in this order, wherein a rod of 10 mmφ is manufactured at a cooling rate of 1° C./s to 20° C./s during casting and rolling, intermediate annealing is performed at 300 to 450° C. for 0.5 to 4 hours during an intermediate heat treatment, and thereafter final annealing is performed at 437° C. to 641° C. for 0.03 to 0.54 hours during a subsequent solution heat treatment. Japanese Patent No. 4986251 discloses a method of manufacturing a 6xxx series aluminum alloy wire in which steps similar to those described above are performed, wherein a rod of 10 mmφ is manufactured at a cooling rate of 1° C./s to 20° C./s during casting and rolling, intermediate annealing is performed at 300 to 450° C. for 0.17 to 4 hours during an intermediate heat treatment, and thereafter final annealing is performed at 415° C. to 633° C. for 0.03 to 0.54 hours during a subsequent solution heat treatment.
Japanese Laid-Open Patent Publication No. 2010-163677 discloses a method of manufacturing a 6xxx series aluminum alloy wire in which steps of casting, wire drawing, intermediate heat treatment, wire drawing and solution (recrystallization) heat treatment are performed in this order, wherein an ingot is manufactured at a cooling rate of 10° C./s to 300° C./s during casting, a heat treatment is performed at 300 to 450° C. for 1 to 4 hours during an intermediate heat treatment, and thereafter a heat treatment is performed at 300° C. to 450° C. for 1 to 4 hours during solution heat treatment. Further, Japanese Laid-Open Patent Publication No. 2010-163676 discloses a method of manufacturing a 6xxx series aluminum alloy wire in which steps of casting, wire drawing, intermediate heat treatment and wire drawing are performed in this order, wherein an ingot is manufactured at a cooling rate of 10° C./s to 300° C./s during casting.
However, with the aluminum alloy wires of Japanese Patent No. 4986252, Japanese Patent No. 4986251, Japanese Laid-Open Patent Publication No. 2010-163677 and Japanese Laid-Open Patent Publication No. 2010-163676, abnormal growth of crystal grains may occur locally during heat treatment in a manufacturing process, and, as a result, there is a drawback that an amount of plastic deformation of an electric wire upon crimping may vary and crimp reliability upon crimping to an object such as a terminal is insufficient.
It is an object of the present disclosure to provide an aluminum alloy conductor wire that has improved crimp reliability while ensuring excellent strength even configured as a fine wire having a wire diameter of less than or equal to 1.5 mm and used as a conductor of an electric wiring structure, as well as an aluminum alloy stranded wire, a coated wire, and a wire harness, and to provide a method of manufacturing an aluminum alloy conductor wire.
The present disclosure is related to providing a manufacturing method and a structure in which, based on a prerequisite that an aluminum alloy containing Mg, Si and Fe is used, controlling a component composition and a manufacturing process, abnormal growth of crystal grains upon recrystallization is uniformly suppressed using a particle pinning effect, and crimp reliability is improved while ensuring excellent strength.